Variable ratio proportioning device

ABSTRACT

A proportioning device for producing a modulated outlet pressure which varies as a predetermined non-linear function of inlet pressure. A pair of opposed pistons are subjected to inlet and outlet pressures respectively and actuate a two-way valve for admitting pressure fluid to the outlet and permitting its return to the inlet. The forces on the pistons include pressure forces and also a biasing force whose value is determined by a third piston subjected to inlet pressure acting on the opposed pistons through a system of levers, a cam, and a spring.

ilnited States Patent 11 1 Holland VARIABLE RATIO PROPORTIONING DEVICE[76] Inventor: Harvison C. Holland, 230 22nd St.,

Santa Monica, Calif. 90402 [22] Filed: July 13, 1970 [21] Appl. No.:54,206

[52] U.S. Cl. 303/6 C, 303/24 F [51] Int. Cl. B60! 8/26 [58] Field ofSearch 303/6 A, 6 C, 13, 303/24 C, 24 F, 28, 40, 57, 61, 86, 21 CG, 24

[56] References Cited 1 UNITED STATES PATENTS 2/1962 Hill et al. 303/24A 5/1967 Hambling et al. 303/24 A 10/1968 Thirion 303/21 CG X 1-June 26,1973 Primary Examiner-Duane A. Reger Attorney-Wolfe, Hubbard, Leydig,Voit & Osann 5 7] ABSTRACT A proportioning device for producing amodulated outlet pressure which varies as a predetermined non-linearfunction of inlet pressure. A pair of opposed pistons are subjected toinlet and outlet pressures respectively and actuate a two-way valve foradmitting pressure fluid to the outlet and permitting its return to theinlet. The forces on the pistons include pressure forces and also abiasing force whose value is determined by a third piston subjected toinlet pressure acting on the opposed pistons through a system of levers,a cam, and aspring.

13 Claims, 6 Drawing Figures PATENIEDJUHZS I973 SHEEIZBFZ Inventor! HARv/so/v C. Ham/v0 Ari-Y3.

- SPEED MPH 1 VARIABLE RATIO PROPORTIONING DEVICE DESCRIPTION OF THEINVENTION The present invention relates to proportioning devices, and inits principal aspect concerns a device for controlling outlet fluidpressure as a predetermined non-linear function of inlet pressure.

A principal object of the present invention is to provide aproportioning device which is effective to provide a predeterminedproportioning function which is not dependent on a simple constantdifferential, or a fixed ratio of pressures, but which will vary theproportioning effect according to a predetermined function of inputpressure which is non-linear. In addition, the function may bediscontinuous at certain points, if required.

Another object is to provide such a device in which the proportioningratio is a non-linear function of input pressure as determined by aspring and a cam shaped lever whose profile is determined by the fluidpressure requirements of the system. A related object is to provide aproportioning device in which a variable biasing force is effective tochange the proportioning ratio.

In greater detail, it is an object of the present invention to provide aproportioning device for use in a motor vehicle in which the ratio ofbraking effect between'front and rear wheels must be varied according todifferent operating conditions in order to achieve the maximum overallbraking effect under differing conditions of tire-road adhesion andvehicle loading without wheel locking and consequent loss of control. Adevice constructed in accordance with the present invention is intendedto take into account tire adhesion to the road surface and vehicleweight-transfer and wheel brake mechanism characteristics duringdeceleration to program optimum proportioning of braking force formaximum vehicle deceleration under all road conditions.

Other objects and advantages of the invention will become apparent uponreading the following detailed specification and upon reference to thedrawings in which:

FIG. 1 is a sectional side elevation of a variable ratio proportioningdevice exemplifying the present inven tion connected in an automotivevehicle braking system;

FIG. 2 is a fragmentary plan view of the bias spring adjusting means ofthe device of FIG. 1;

FIG. 3 is a vertical side elevation on a reduced scale of the devicetaken from the right side of FIG. 1;

FIG. 4 is a graph showing both design and performance input vs. outputpressure curves for a device constructed as shown in FIGS. 1-3;

FIG. 5 is a graph showing stopping distances at different vehicle speedsfor an automobile having a braking system equipped with a deviceconstructed as shown in FIG. 1 and also showing stopping distances forthe same automobile not so equipped; and

FIG. 6 is a view similar to FIG. 1 of a modified device in analternative braking system arrangement.

Although the device of the present invention is shown in connection withparticular exemplary embodiments, it should be understood that theinvention is not to be so limited to the particular embodiments shownand described herein, but is on the contrary applicable to allapplications and uses in which a proportioning device is required todistribute pressure according to a predetermined non-linear function ofinput pressure, rather than in a simple fixed ratio or with a constantpressure diflerential as with prior art designs. While the device of thepresent invention is capable of producing such results, its advantageousfeatures are best utilized in providing a proportioning function whichfollows a complex relationship with inlet pressure.

The device of the present invention is most advantageously used inconnection with a motor vehicle (not shown) having front and rearwheels, each set of wheels being equipped with brakes hydraulicallyactuated by means for generating hydraulic pressure. In a conventionalautomobile having four wheels, with brakes at front and rear, it can beshown that for each distribution of disposable load there is only oneoptimum ratio of braking forces between front and rear for a givencoefficient of friction between the tires and the road which willprovide maximum deceleration and that this optimum ratio varies withchanges in coefficient of friction in a non-linear manner.

The braking force obtainable from the front wheels is enhanced duringbraking due to the weight-transfer effect which tends to increase thedownward force at the front wheels and lessen the force at the rearwheels even though the total downward force of the vehicle on its wheelsis the same as when standing still. Since the maximum braking forceobtainable from a given wheel is equal to the downward force on thewheel times the coefficient of friction between the tire and the road,it can be seen that the front wheels can provide a greater proportion ofthe total braking force, and the rear wheels a lesser proportion as themaximum adhesion obtainable between the tires and the road increases.

For any distribution of disposable load in the vehicle, at eachcoefficient of friction between the tire and the road, there is a singlevalue of braking force that can be applied to the front and acorresponding value of braking force that can be applied to the rearwheels to achieve maximum deceleration of the vehicle without resultingloss of adhesion between the tires and the road with resulting skiddingcoupled with the possibility of loss of control. Under dry, paved roadconditions the ratio of front-to-rear braking force is at a maximum.Under other conditions, such as on wet pavement or ice, a lowercoefficient of friction will be observed, resulting in differentweight-transfer effect and, consequently, different distribution ofdownward tire forces between front and rear, even though the totaldownward force of the vehicle remains the same. It can, therefore, beseen that the proportioning of braking force between front and rearwhich is most effective under one condition will not be correct foranother condition where a different coefficient of friction isencountered. If a braking systemis set up to proportion front-to-rearforces to give maximum braking undermaximum tire-road frictionconditions, with a relatively larger proportion of braking force appliedto the front wheels, the use of the same ratio under low frictionconditions such as on ice covered pavement will result in an excessiveproportion of braking force at the front wheels and consequentunderutilization on the rear wheels or sliding or skidding of the frontwheels before the rear wheels are utilized to maximum braking effect. Onthe other hand, if the fixed proportion is set up to favor lowerfriction conditions, then an attempted maximum stop under more favorablefriction conditions will result in exceeding the adhesion capability ofthe rear tires by producing a greater proportion of braking force thanthey can accommmodate without skidding. This results not only in morethan the optimum stopping distance for the vehicle, but also increasesthe danger of losing control of the vehicle because the skidding rearwheels will tend to induce a spin.

In modern passenger automotive vehicles hydraulic brakes are usedexclusively. By the simultaneous application of fluid pressure from amaster cylinder to individual slave cylinders in the brake mechanism ofeach wheel, the brakes are applied concurrently providing equal ordirectly proportional braking forces at the front and rear wheelsdepending upon the relative size of the front and rear slave cylinders.It is also common practice to separate the hydraulic systems betweenfront and rear to assure the operation of one pair of brakes in case theother hydraulic system fails. However, in these split systems,mechanical interconnection of the two hydraulic systems is provided toassure substantially equal front and rear pressures. Occasionallypressure limiting devices and other means have been inserted in the rearbrake system to limit maximum rear brake system pressure, or otherwisemodify the front to rear braking force relationship in some arbitrarymanner. These pressure limiting devices produce a noncontinuousfront-to-rear brake force relationship. Since the ratio of front-to-rearbraking forces (and consequent hydraulic pressures) required for maximumvehicle deceleration on various types of road friction surfaces does notvary linearly with the tire coefficient of friction, and is acontinuously varying ratio, none of these systems can provide optimumbraking effect except at one or two values of coefficient of friction,and must necessarily produce non-optimum results for all other roadconditions.

For a given vehicle configuration for each loading condition, the frontand rear braking forces required for maximum deceleration may bedetermined as a function of tire coefficient of friction. Determinationof the weight-transfer effect as well as the method of designing abraking system to match these optimum requirements is described in myco-pending patent application Ser. No. 708,880, filed Feb. 28, 1968 forMETHOD FOR PRODUCING MAXIMUM VEHICLE DECELERATION. For a givenconfiguration of wheel brake mechanisms including front and rear slavecylinder sizes, optimum values of concurrent front and rear hydraulicsystem pressure may now be established for each value of the coefficientof friction between the tires and the road for maximum deceleration,under each loading condition. It will be observed (see my copendingpatent application Ser. No. 708,880) that these pressures are not simplestraight line relationships, but rather a family of continuous curves ofa more complex nature. The values of hydraulic pressure are determinedby the configuration of the vehicle in terms of wheel base, center ofgravity including load distribution, and wheel brake mechanism and notby any arbitrary equalization, or non-equalization factor, within thebraking system for proportioning the braking forces between front andrear. For simplification, it may be desirable to use equal front andrear hydraulic pressures near the low tire friction end where theoptimum hydraulic pressures are substantially equal.

Obtaining the optimum pressure relationships described above for thehydraulic brakes of a motor vehicle is achieved, according to thepresent invention, by a proportioning device herein shown as a valve inFIGS. l-3. The device includes a housing 10 having a high pressure inlet12 and a regulated pressure outlet 14, the outlets each being equippedwith hydraulic fittings as customarily employed on automobile hydraulicbrake systems. The high pressure inlet 12 is supplied by the mastercylinder in a single master cylinder system (not shown), or as in thesplit system illustrated in FIG. 1 by the rear wheel system mastercylinder 16. Pressure fluid from the front wheel system master cylinder18 is applied directly to the front wheel brakes 20, while pressurefluid from the regulated outlet 14 is applied to the rear wheel brakes22. The housing 10, is shown in FIG. 3 attached to the firewall 23 ofthe vehicle, by screws 23', but may be attached at any convenientlocation.

According to the present invention, the fluid pressure supplied to therear brakes 22 from the regulated outlet 14 is varied according to apredetermined function of the rear brake line pressure supplied from themaster cylinder to the high pressure inlet 12, so as to vary the brakingeffect between front and rear wheels as vehicle deceleration changes. Inkeeping with the invention, the device is effective to vary the ratio ofthe brake line pressures between the front and rear brake lines as anon-linear function of vehicle deceleration. This function ispredetermined, according to the method described in my co-pendingapplication, to take into account the weight and center of gravitycharacteristics of the vehicle, and the braking characteristics of thewheel brake mechanism with which the vehicle is equipped, in order tothereby obtain optimum proportioning of braking force for maximumbraking under all road conditions.

In carrying out the present invention, the ratio of front-to-rear brakeline pressures is varied by regulating means, herein shown in FIGS. l-3including a valve for regulating the fluid pressure in the outlet 14 tothe rear brake line. This regulation means is concurrently responsive topredetermined tire adhesion and weight transfer characteristics of thevehicle, and front and rear wheel brake mechanism characteristic of thevehicle. To this end, from the high pressure inlet 12, pressure fluid isdirected through a conduit 24 into a first cylinder 26 containing apiston 28. Another conduit 30 carries high pressure fluid into a checkvalve chamber 32 containing a ball check valve 34 urged by a spring 36into sealing contact with an opening 38 forming a seat for the ball andleading to a regulated pressure cylinder 40 containing a second piston42. From the regulated pressure cylinder 40 a conduit 44 which bypassesthe high pressure conduit 30 connects to the regulated pressure outlet14. Both pistons 28, 42 are provided with seals 46 made of teflon orother low friction material and in the illustrated embodiment thepistons 28, 42 are constructed as a single coaxial piston shuttle 48with the pressure faces of the pistons being oppositely disposed and ofequal size so that the pressure forces on the shuttle from the highpressure cylinder 26 and the regulated pressure cylinder 40 are indirect opposition.

A pin 50 is carried by the second piston 42 which contacts the checkvalve ball 34. With the structure shown, high pressure forces on thefirst piston 28 tend to urge the piston shuttle 48 to the right whileregulated pressure forces in the pressure cylinder 40 acting on thesecond piston 42 tend to urge the second piston 42 and thus the pistonshuttle 48 to the left. In addition, when the ball 34 is seated, aresultant force tending to retain ball 34 on its seat 38 (due to highfluid pressure in the chamber 32, regulated fluid pressure in thechamber 40, and spring force from the spring 36) acts on the pistonshuttle 48 through the pin 50 and tends to urge the piston shuttle 48 tothe left. It will be observed that when the inlet pressure forces on thefirst piston 28 exceed the regulated pressure forces on the secondpiston 42 (and the resultant force on the ball 34) the piston shuttle 48will be displaced to the right as seen in FIG. 1, moving the ball 34 offits seat 38 and allowing high pressure fluid from the conduit 30 to passthrough the conduit 44 to the regulated pressure outlet 14.

The structure described thus far, without the addition of other elementsof the invention, would operate in a known manner as a fixed ratioproportioning valve, with the ratio of pressures between the inlet 12and outlet 14 being determined substantially by the ratio of theeffective pressure areas of the pistons 28, 42 (in this case unity).Pursuant to'the invention, however, there is provided means herein shownas a piston, spring, cam lever and connecting means assembly forapplying a variable biasing force to the piston shuttle 48, for varyingthe proportioning ratio, and thus the front to rear braking effect as afunction of front brake system pressure; the piston, spring, cam leverand connecting means assembly applies a predetermined non-linear biasingforce which is representative of tire adhesion, weight-transfer, andwheel brake mechanism characteristics of the vehicle. This isaccomplished, in the present case, by providing a conduit extension 52carrying inlet pressure, equal to (or having a known relationship to)front wheel brake system pressure, to a third cylinder 54 containing athird piston 56. The third piston 56 has a low friction seal 58 ofteflon or like material similar to the seals on the first and secondpistons, and is received at its opposite end in a low friction bushing60 in the housing so it is freely slidable in the housing.

Pivoted to the third piston 56 is a cam lever arm 62. The cam lever arm62 has at one end a hook 64 to which a biasing spring 66 is attached. Atthe other end, the cam lever arm 62 has a cam surface 68 which is urgedby the biasing spring 66 against a connecting means consisting of aslotted lever arm 70 which is pivoted on a pin 72 attached to thehousing 10 and applies a variable biasing force to the piston shuttle48.

With a vehicle of known size, weight, load distribution and wheel brakemechanism, a biasing spring 66 is selected and the the shape of the camsurface 68 on the cam lever arm 62 is determined so that the contactpoint of engagement with the slotted lever arm 70 is moved in responseto front wheel brake system pressure represented by the motion of thethird piston 56 in a manner which varies the biasing force applied tothe piston shuttle 48. In this way, the front and rear brake pressuresare varied as necessary to match the previously determined optimum frontand rear brake pressure relationship and thereby match the optimumconcurrent braking forces for both front and rear wheels during allconditions of maximum braking effort, according to the coefficient offriction available at the road surface.

To connect the slotted lever arm with the piston shuttle 48 in a mannerthat allows free and easy motion of the piston shuttle, the lever arm 70is preferably constructed with a tapering tip terminating in a ball 73which is received within a bore 74 in the slidable piston shuttle 48.The biasing spring 66 is anchored to the housing 10 on a support bar 76,and exerts a force tending to move the cam lever arm 62 clockwise asseen in FIG. 1. The cam surface 68 of the cam arm 62 is thus urged tothe right, and (in the position shown in solid lines) contacts theslotted lever arm 70 at point A. The slotted lever arm 70 is therebyurged in a counterclockwise direction, urging the pistons shuttle 48 tothe left and reducing the force tending to unseat the ball 34.

In operation, with a relatively low initial inlet hydraulic pressurerepresenting low manual effort on the brake pedal and low total brakingforces, the piston, spring, cam lever and connecting means elements willassume the positions shown in solid lines in FIG. 1, with the contactpoint being at A. It can be seen from FIG. 1 that in this position themechanical advantage of the biasing spring 66 in acting to move thepiston shuttle 48 to the left is small, because the contact point A istoward the tip of the cam lever arm 62, and near the pivot of theslotted lever arm 70. At higher pressures representing high totalbraking forces, however, the third piston 56 will move to the right asseen in FIG. 1, shifting the cam lever arm 62 to some alternate positionas indicated in phantom and moving the contact point to B. Here thecontact point is in a position which gives the biasing spring 66 agreater mechanical advantage in urging the piston shuttle 48 to theleft, increasing the biasing force by an amount greater than theincrease in the force of the spring 66 and thus the proportioning of thehydraulic pressures achieved by the device will be correspondinglydifferent. As the biasing force on the piston shuttle 48 is enhancedthrough the movement of the third piston 56 to the right under increasedinlet pressure, the ratio of inlet to outlet pressures will becomegreater; that is, the outlet pressure to the vehicles rear brakes willbe diminished in a non-linear manner as a function of total brakingforces.

As a further feature of the invention, means are provided for adjustmentof the proportioning ratio for different vehicle loadings, herein shownas means for selectively adjusting the biasing force through the use ofa rotatable end cap 77 carried on a cylindrical extension 78 of thehousing 10 in which the biasing spring 66 is contained. The bar 76 towhich the biasing spring 66 is attached extends through a pair ofelongate slots on opposite sides of the cylindrical body extension 78 asshown in FIG. 2 and is movable axially therein. The rotatable end cap 77contains similar elongate slots 82, but these are disposed at an angleto the slots 80 in the housing extension 78 so that rotation of the endcap 77 cams the bar 76 axially according to the direction of caprotation. If desired, rotation of the end cap 77 may lever arm 70 to itsfull clockwise position thus moving the piston shuttle 48 to the rightin FIG. 1 and lifting the check valve ball 34 from its seat. Aftercompleting air bleeding operations, screw 86 is partially withdrawnuntil it clears slotted lever arm 70 in all positions and is thenretained in this position by tightening locknut 88.

A proportioning device constructed according to this invention issuitable for use in an automotive vehicle brake system provided with aconventional master cylinder having a single plunger (not shown)connected to a brake pedal for direct actuation. In such case, the highpressure inlet 12 of the device is supplied from the brake line leadingfrom the master cylinder to the front wheel brakes, and the regulatedpressure outlet 14 is connected to the rear wheel brake. The device isthus effective to vary the proportioning ratio between the fluidpressure applied to the front wheel brakes, and the fluid pressureapplied to the rear wheel brakes, in accordance with a predeterminedfunction of inlet pressure dependent upon tire adhesion, weight transferand wheel brake mechanism characteristics of the vehicle, as defined bythe spring 66 and the profile of the cam surface 68. Further, a numberof similar front and rear fluid pressure proportioning ratio programsare formed by the operation of the end cap 77 to match the requirementscaused by variations in disposable load in the vehicle.

While the master cylinder of FIG. 1 is shown directly manually actuated,it will be understood that the device of the present invention is suitedfor installation in a power brake system, as for example an automotivebraking system provided with a power booster controlled by the brakepedal and connected for operating a master cylinder or having oneincorporated therein, or a full power system in which the hydraulicpressure is supplied by a power operated pump and controlled by amanually operated valve.

In the form of the device shown in FIG. 1, the front and rear brakingsystems are completely separate; the device contained in housing islocated within the rear braking system; and in the event of loss offluid in one system, the other will be available to stop the vehicleupon brake pedal actuation. For example, should the front system losefluid and become inoperative, it will be observed that the device willcontinue to operate and will supply a diminished pressure to the rearwheel brakes which is a function of inlet pressure. This diminishedfluid pressure will still be effective to operate the rear brakes tostop the vehicle. This is the preferred configuration since, when onlythe rear brakes are operative, there is a tendency on the part of theoperator to apply excessive force to the brake pedal and thus slide thewheels.

Referring now to FIG. 6, an alternative form of the invention is shown,involving a variable proportioning device contained in housing 10' in asplit system (as in FIG. 1) with separate front and rear braking systemssupplied by master cylinder pistons of a dual master cylinder.

In the form of device contained in housing 10 shown in FIG. 6, thedevice is located in both front and rear braking systems, although thereis no hydraulic flow connection between the systems, and thus theirseparation hydraulically is maintained. In the event of loss of fluidpressure in the front braking system in such an arrangement, piston 56will not be actuated and the rear braking system will receive fullmaster cylinder pressure, rather than a diminished pressure as in thecase of the form of the invention shown in FIG. 1.

Referring specifically to FIG. 6, the device contained in housing 10' isessentially the same construction shown in FIG. 1, with the exceptionsthat a hydraulic inlet is provided to supply pressure fluid through aconduit 92 directly to the pressure control piston 56 from the frontbraking system 20, and the passage 52 which is used to convey pressurefluid to the control piston from the high pressure inlet in the deviceof FIG. 1 is blocked by means herein shown as a plug 100. By blockingthis passage, the front and rear braking systems 20, 22 are maintainedseparate for independent operation in case of loss of hydraulic fluid ineither system. But with this arrangement, in the event of loss of frontbrake line pressure, the spring 66 (see also F IG. 1) becomes effectiveto move the control piston 56 to the left causing the contact point ofengagement A between the cam surface 68 on the cam lever arm 62 to moveto the tip of the cam lever arm 62 and near the pivot of the slottedlever arm 70. In this position, as in the condition of low manual efforton the brake pedal and low total braking forces, the piston, spring, camlever anc connecting means elements will assume the positions shown insolid lines in FIG. 6, and the mechanical advantage of the biasingspring 66 in acting to move the piston shuttle 48 to the left is small.As the pressure produced by the rear brake master cylinder increases,since it acts directly on the first piston 28 through the high pressureinlet of the device contained in housing 10', the increasing pressurewill shift the piston shuttle 48 to the right, in effect holding theball valve 34 open and supplying substantially full master cylinderpressure to the rear braking system 22.

Now turning to FIGS. 4 and 5, these are graphs depicting, in the case ofFIG. 4, design and performance input vs. output pressure curves for adevice constructed as shown in FIG. 1 and illustrating the nonlinearpressure relationship and the low hysteresis in the operation of thedevice; and in the case of FIG. 5, stopping distances at differentspeeds for a vehicle having a braking system with and without a deviceconstructed as shown in FIG. 1.

Referring to FIGS. 4 and 5, a device was constructed as shown in FIG. 1for use in the braking system of a 1968 Ford Mustang. The steps of themethod described in my co-pending application Ser. No. 708,880 entitledMETHOD FOR PRODUCING MAXIMUM VEHI- CLE DECELERATION were followed.Having determined the weight-transfer characteristics of this vehicleand the pressure-braking force characteristics of its braking system, acam profile 68 for this particular automobile was calculated to produce,in the operation of the device, ratios of front-to-rear braking pressureat different values of rear brake line pressure which obtain optimumbraking effect for both front and rear wheels according to thecoefficient of friction available at the road surface. These pressuresare shown as the middle of the three curves of FIG. 4 and are the designpoint values for the device.

The fluid pressures controlled by the device will lie within ahysteresis band caused by the delay in opening and closing the checkvalve ball 34 due to the resultant forces on the ball 34 and to frictioninherent in all moving mechanisms. Based on pressure, spring andfriction force data for the parts of the device, the upper and lowercurves were added to FIG. 4 to define the hysteresis band within whichthe device should operate. Upon completion, the device was tested andconfirmed both the non-linearity of the performance curve and thenarrowness of the hysteresis band. The test points shown on FIG. 4 wererandom points taken without regard for increasing or decreasingpressure. The rotatable end cap 76 was in the mid-position thus placingthe biasing spring 66 in the design point position. Other tests showedthat rotating the end cap increased or decreased the level of thehysteresis band in direct proportion to the inlet pressure withoutchanging its width.

The device was installed in the braking system of the 1968 Mustang andtests conducted to determine the minimum possible stopping distance on agiven section of dry paved roadway with and without the deviceoperating. Since stopping distance is proportional to velocity squared,FIG. 5 is plotted on a log-log scale to permit connecting points with astraight line for maximum accuracy. Values shown in FIG. 5 are thelowest obtainable without sliding the tires from a number of runs ateach speed. (Sliding tires increase stopping distance and produce lossof control.) Curve A shows results comparable to those obtainable with amanufacturers standard brake system, these results being obtained byblocking the check valve ball 34 in the open position. Curve B shows theresults obtained with the proportioning device of the present inventionfully operative. Distances were measured by means of an AmericanAutomobile Association inertia type detonator marked and a steel tapeline. Speeds were measured by the standard automobile speedometer whichwas calibrated by stop watch against an officially measured mile ofhighway before and after testing. A 26 percent reduction in stoppingdistance when the device is operative is shown.

I claim as my invention:

1. A variable ratio proportioning device comprising in combination: ahousing containing a piston and cylinder connected to an inlet forpressure fluid on one side and to an outlet for pressure fluid on theother side; means for applying a biasing force to the piston; means forvarying the magnitude of the biasing force as a predetermined,non-linear function of the inlet fluid pressure; and means controlled bysaid piston for admitting fluid from the inlet to the outlet of thedevice and providing an outlet fluid pressure which varies according tosaid predetermined, nonlinear function of the inlet fluid pressure.

2. A variable ratio proportioning device comprising in combination: ahousing containing a first piston and cylinder connected to an inlet forpressure fluid, a second piston and cylinder connected to an outlet forpressure fluid, said pistons being oppositely disposed with inlet fluidpressure force on the first pistonacting in opposition to the outletfluid pressure force on the second piston; means for applying a biasingforce to the first piston modifying the inlet fluid pressure forceacting thereon; means for varying the magnitude of thebiasing force as anon-linear function of the inlet fluid pressure; valve means foradmitting pressure fluid from the inlet to the outlet; and meansconnecting the second piston to open the valve means when the fluidpressure force plus biasing force on the first piston exceeds the fluidpressure force on the second piston, so that the outlet pressure variesas a non-linear function of the inlet fluid pressure.

3. A device as defined in claim 2 in which the valve means consists of aball check valve seating against an opening leading to the secondcylinder, and the means for opening the valve means including a pinlocated in said opening for urging the ball from its seat, said pinbeing actuated by relative motion of the piston and the cylinder.

4. A device as defined in claim 2 in which the means for applying andvarying a biasing force includes a baising spring, and a third pistonand cylinder connected to the inlet, said third piston carrying a firstpivoted lever arm connected at one end to the biasing spring and at theother end to connecting means for transferring said biasing force to thesecond piston.

5. A device as defined in claim 4 in which the connecting means includesa second pivoted lever arm contacting the first and second pistons andthe first lever arm with one of said lever arms having a cam surface ofpredetermined profile at the contact point, whereby said contact pointis shifted with respect to the pivots of the first and second lever armsaccording to displacement of the third piston to vary the biasing forceaccording to the inlet fluid pressure force as modified by theinteraction of the biasing spring and the cam profile.

6. A device as defined in claim 4 in which the end of the said biasingspring opposite the first lever arm is carried on an anchor in thehousing, and including adjustment means for selectively adjusting theposition of the anchor whereby the force of the biasing spring at anyposition of the said third piston may be varied for modifying the outletfluid pressure characteristics of the device.

7. A device as defined in claim 6 in which the anchor consists of a barretained in an elongate slot in a cylindrical portion of the housing,and the adjustment means includes a rotatable end cap receiving said barin an elongate slot at an angle to the slot in the housing, said caphaving calibrations whereby rotation of the cap is effective to adjustthe position of the bar for varying the force of the biasing springaccording to predetermined values.

' 8. For use on a vehicle having front and rear wheels and given tireadhesion and weight-transfer characteristics on braking, given vehicleloading, and front and rear fluid pressure operated brakes for brakingthe wheels, a proportioning device as defined in claim 1 in which theinlet is connected to the front brakes and the outlet is connected tothe rear brakes, and in which the said means for varying the biasingforce includes a cam and defines the non-linear function by which theoutlet fluid pressure varies from the inlet fluid pressure, said camhaving a profile which is predetermined according to the given tireadhesion, weight-transfer and front and rear brake mechanismcharacteristics of the vehicle.

9. For use on a vehicle having front and rear wheels and given tireadhesion and weight-transfer characteristics on braking, given vehicleloading, and front and rear fluid pressure operated brakes for brakingthe wheels, a proportioning device as defined in claim 6, in which theinlet receives fluid at a pressure varying as a function of front brakepressure fluid, the outlet supplies pressure fluid to said rear brakes,and said piston, spring, cam lever and connecting means elements definethe non-linear function by which the outlet fluid pressure varies fromthe inlet fluid pressure, said cam lever having a profile which ispredetermined according to the given tire adhesion, weight-transfer andfront and rear brake mechanism characteristics of the vehicle and saidbias spring adjusting means being provided for further modifying outletfluid pressure according to the given vehicle loading.

10. In a vehicle brake system having fluid pressure generating means,front and rear wheel brakes, and front and rear brake lines fortransmitting fluid pressure to said front and rear wheel brakesrespectively from said pressure generating means: a pressureproportioning device connected in said rear brake line, said deviceincluding regulating means for regulating the fluid pressure transmittedthrough said rear brake line to said rear wheel brakes as apredetermined nonlinear function of fluid pressure supplied from saidfluid pressure generating means, said predetermined functionrepresenting tire adhesion, weight-transfer and front and rear wheelbrake mechanism characteristics of the vehicle, said regulating meansbeing operable to regulate the fluid pressure in said rear brake line soas to increase the ratio of front to rear braking effort upon increasein total braking force according to said predetermined function.

11. In a vehicle brake system having front and rear master cylinders,front and rear wheel brakes, and front and rear brake lines fortransmitting fluid pressure to said front and rear wheel brakesrespectively from said front and rear master cylinders: a pressureproportioning device connected in said rear brake line, said deviceincluding regulating means for regulating the fluid pressure transmittedthrough said rear brake line to said rear wheel brakes as apredetermined non-linear function of fluidpressure supplied from saidrear master cylinder, said predetermined function representing tireadhesion, weight-transfer and front and rear wheel brake mechanismcharacteristics of the vehicle, said regulating means being operable toregulate the fluid pressure transmitted to said rear brake line so as toincrease the ratio of front to rear braking effort upon increase intotal braking force according to said predetermined function.

12. In a vehicle brake system having front and rear master cylinders,front and rear wheel brakes, and front and rear brake lines fortransmitting pressure fluid to said front and rear wheel brakesrespectively from said front and rear master cylinders; a pressureproportioning device including regulating means concurrently responsiveto predetermined tire adhesion and weighttransfer characteristics of thevehicle and front and rear wheel brake mechanism characteristics of thevehicle, said regulating means being operable to regulate the fluidpressure in said rear brakes so as to increase the ratio of front torear braking effort upon increase in total braking force as a functionof said characteristics under normal operating condition, and meansresponsive to a loss in front brake line pressure for shifting saidregulating means to pass substantially full rear brake line pressure tosaid rear wheel brakes.

13. In a proportioning device for regulating an outlet fluid pressure ofthe type comprising a housing having an inlet passage for receiving andreturning a pressure fluid, the pressure of which is variable, an outletpassage for receiving and returning pressure fluid, a regulating checkvalve controlling fluid flow between the inlet passage and the outletpassage, and arranged to close against the flow to the outlet passageand permit flow by opening of the valve from the outlet to the inlet;the improvement of a dual piston cooperating with the valve and havingopposed reaction areas subjected to the fluid pressures in the inlet andoutlet passages, and a variable resilient biasing means constructed andarranged to react on the piston in opposition to the inlet fluidpressure, including a second single piston having a third control area,the movement of which controls the programming of a number ofpredetermined nonlinear inlet to outlet fluid pressure relationshipsthrough the action of said biasing means.

1. A variable ratio proportioning device comprising in combination: ahousing containing a piston and cylinder connected to an inlet forpressure fluid on one side and to an outlet for pressure fluid on theother side; means for applying a biasing force to the piston; means forvarying the magnitude of the biasing force as a predetermined,non-linear function of the inlet fluid pressure; and means controlled bysaid piston for admitting fluid from the inlet to the outlet of thedevice and providing an outlet fluid pressure which varies according tosaid predetermined, nonlinear function of the inlet fluid pressure.
 2. Avariable ratio proportioning device comprising in combination: a housingcontaining a first piston and cylinder connected to an inlet forpressure fluid, a second piston and cylinder connected to an outlet forpressure fluid, said pistons being oppositely disposed with inlet fluidpressure force on the first piston acting in opposition to the outletfluid pressure force on the second piston; means for applying a biasingforce to the first piston modifying the inlet fluid pressure forceacting thereon; means for varying the magnitude of the biasing force asa non-linear function of the inlet fluid pressure; valve means foradmitting pressure fluid from the inlet to the outlet; and meansconnecting the second piston to open the valve means when the fluidpressure force plus biasing force on the first piston exceeds the fluidpressure force on the second piston, so that the outlet pressure variesas a non-linear function of the inlet fluid pressure.
 3. A device asdefined in claim 2 in which the valve means consists of a ball checkvalve seating against an opening leading to the second cylinder, and themeans for opening the valve means including a pin located in saidopening for urging the ball from its seat, said pin being actuated byrelative motion of the piston and the cylinder.
 4. A device as definedin claim 2 in which the means for applying and varying a biasing forceincludes a baising spring, and a third piston and cylinder connected tothe inlet, said third piston carrying a first pivoted lever armconnected at one end to the biasing spring and at the other end toconnecting means for transferring said biasing force to the secondpiston.
 5. A device as defined in claim 4 in which the connecting meansincludes a second pivoted lever arm contacting the first and secondpistons and the first lever arm with one of said lever arms having a camsurface of predetermined profile at the contact point, whereby saidcontact point is shifted with respect to the pivots of the first andsecond lever arms according to displacement of the third piston to varythe biasing force according to the inlet fluid pressure force asmodified by the interaction of the biasing spring and the cam profile.6. A device as defined in claim 4 in which the end of the said biasingspring opposite the first lever arm is carried on an anchor in thehousing, and including adjustment means for selectively adjusting theposition of the anchor whereby the force of the biasing spring at anyposition of the said third piston may be varied for modifying the outletfluid pressure characteristics of the device.
 7. A device as defined inclaim 6 in which the anchor consists of a bar retained in an elongateslot in a cylindrical portion of the housing, and the adjustment meansincludes a rotatable end cap receiving said bar in an elongate slot atan angle to the slot in the housing, said cap having calibrationswhereby rotation of the cap is effective to adjust the position of thebar for varying the force of the biasing spring according topredetermined values.
 8. For use on a vehicle having front and rearwheels and given tire adhesion and weight-transfer characteristics onbraking, given vehicle loading, and front and rear fluid pressureoperated brakes for braking the wheels, a proportioning device asdefined in claim 1 in which the inlet is connected to the front brakesand the outlet is connected to the rear brakes, and in which the saidmeans for varying the biasing force includes a cam and defines thenon-linear function by which the outlet fluid pressure varies from theinlet fluid pressure, said cam having a profile which is predeterminedaccording to the given tire adhesion, weight-transfer and front and rearbrake mechanism characteristics of the vehicle.
 9. For use on a vehiclehaving front and rear wheels and given tire adhesion and weight-transfercharacteristics on braking, given vehicle loading, and front and rearfluid pressure operated brakes for braking the wheels, a proportioningdevice as defined in claim 6, in which the inlet receives fluid at apressure varying as a function of front Brake pressure fluid, the outletsupplies pressure fluid to said rear brakes, and said piston, spring,cam lever and connecting means elements define the non-linear functionby which the outlet fluid pressure varies from the inlet fluid pressure,said cam lever having a profile which is predetermined according to thegiven tire adhesion, weight-transfer and front and rear brake mechanismcharacteristics of the vehicle and said bias spring adjusting meansbeing provided for further modifying outlet fluid pressure according tothe given vehicle loading.
 10. In a vehicle brake system having fluidpressure generating means, front and rear wheel brakes, and front andrear brake lines for transmitting fluid pressure to said front and rearwheel brakes respectively from said pressure generating means: apressure proportioning device connected in said rear brake line, saiddevice including regulating means for regulating the fluid pressuretransmitted through said rear brake line to said rear wheel brakes as apredetermined non-linear function of fluid pressure supplied from saidfluid pressure generating means, said predetermined functionrepresenting tire adhesion, weight-transfer and front and rear wheelbrake mechanism characteristics of the vehicle, said regulating meansbeing operable to regulate the fluid pressure in said rear brake line soas to increase the ratio of front to rear braking effort upon increasein total braking force according to said predetermined function.
 11. Ina vehicle brake system having front and rear master cylinders, front andrear wheel brakes, and front and rear brake lines for transmitting fluidpressure to said front and rear wheel brakes respectively from saidfront and rear master cylinders: a pressure proportioning deviceconnected in said rear brake line, said device including regulatingmeans for regulating the fluid pressure transmitted through said rearbrake line to said rear wheel brakes as a predetermined non-linearfunction of fluid pressure supplied from said rear master cylinder, saidpredetermined function representing tire adhesion, weight-transfer andfront and rear wheel brake mechanism characteristics of the vehicle,said regulating means being operable to regulate the fluid pressuretransmitted to said rear brake line so as to increase the ratio of frontto rear braking effort upon increase in total braking force according tosaid predetermined function.
 12. In a vehicle brake system having frontand rear master cylinders, front and rear wheel brakes, and front andrear brake lines for transmitting pressure fluid to said front and rearwheel brakes respectively from said front and rear master cylinders; apressure proportioning device including regulating means concurrentlyresponsive to predetermined tire adhesion and weight-transfercharacteristics of the vehicle and front and rear wheel brake mechanismcharacteristics of the vehicle, said regulating means being operable toregulate the fluid pressure in said rear brakes so as to increase theratio of front to rear braking effort upon increase in total brakingforce as a function of said characteristics under normal operatingcondition, and means responsive to a loss in front brake line pressurefor shifting said regulating means to pass substantially full rear brakeline pressure to said rear wheel brakes.
 13. In a proportioning devicefor regulating an outlet fluid pressure of the type comprising a housinghaving an inlet passage for receiving and returning a pressure fluid,the pressure of which is variable, an outlet passage for receiving andreturning pressure fluid, a regulating check valve controlling fluidflow between the inlet passage and the outlet passage, and arranged toclose against the flow to the outlet passage and permit flow by openingof the valve from the outlet to the inlet; the improvement of a dualpiston cooperating with the valve and having opposed reaction areassubjected to the fluid pressures in the inlet and outlet passages, and avarIable resilient biasing means constructed and arranged to react onthe piston in opposition to the inlet fluid pressure, including a secondsingle piston having a third control area, the movement of whichcontrols the programming of a number of predetermined non-linear inletto outlet fluid pressure relationships through the action of saidbiasing means.